Raffaele Scicchitano

Elevated Nerve Growth Factor Levels in the Synovial Fluid of Patients with Inflammatory Joint Disease

A novel pH shock extraction procedure was used to measure nerve growth factor (NGF) levels in both normal and inflamed synovial fluids using a sensitive and specific two-site enzyme linked immunosorbant assay. To date no data is available on NGF levels in normal synovial fluids. Synovial fluids were taken from 5 normal volunteers, 12 patients with rheumatoid arthritis and 10 patients with other inflammatory arthropathies. The mean ± SEM NGF concentration in normal synovial fluids was 95 ± 33.2 pg/ml (range 39.1–143.1 pg/ml), whereas the mean NGF concentration in the synovial fluids taken from patients with rheumatoid arthritis was 532.5 ± 123.8 pg/ml (range 152–1686 pg/ml). The mean NGF concentration in patients with other inflammatory arthropathies was also raised (430.6 ± 90 pg/ml; range 89–1071 pg/ml). The NGF concentrations were significantly higher in the synovial fluids from both inflamed groups (ANOVA p < 0.05) compared to normals. Raised levels of NGF in synovial fluid may contribute directly to joint inflammation via activation of inflammatory cells.

Exercise-induced hypoxaemia in highly trained cyclists at 40% peak oxygen uptake

Abstract A group of 15 competitive male cyclists [mean peak oxygen uptake, V˙O2peak 68.5 (SEM 1.5 ml · kg−1 · min−1)] exercised on a cycle ergometer in a protocol which began at an intensity of 150 W and was increased by 25 W every 2 min until the subject was exhausted. Blood samples were taken from the radial artery at the end of each exercise intensity to determine the partial pressures of blood gases and oxyhaemoglobin saturation (SaO2), with all values corrected for rectal temperature. The SaO2 was also monitored continuously by ear oximetry. A significant decrease in the partial pressure of oxygen in arterial blood (PaO2) was seen at the first exercise intensity (150 W, about 40% V˙O2peak). A further significant decrease in PaO2 occurred at 200 W, whereafter it remained stable but still significantly below the values at rest, with the lowest value being measured at 350 W [87.0 (SEM 1.9) mmHg]. The partial pressure of carbon dioxide in arterial blood (PaCO2) was unchanged up to an exercise intensity of 250 W whereafter it exhibited a significant downward trend to reach its lowest value at an exercise intensity of 375 W [34.5 (SEM 0.5) mmHg]. During both the first (150 W) and final exercise intensities (V˙O2peak) PaO2 was correlated significantly with both partial pressure of oxygen in alveolar gas (PAO2, r = 0.81 and r = 0.70, respectively) and alveolar-arterial difference in oxygen partial pressure (PA−aO2, r = 0.63 and r = 0.86, respectively) but not with PaCO2. At V˙O2peakPaO2 was significantly correlated with the ventilatory equivalents for both oxygen uptake and carbon dioxide output (r = 0.58 and r = 0.53, respectively). When both PAO2 and PA−aO2 were combined in a multiple linear regression model, at least 95% of the variance in PaO2 could be explained at both 150 W and V˙O2peak. A significant downward trend in SaO2 was seen with increasing exercise intensity with the lowest value at 375 W [94.6 (SEM 0.3)%]. Oximetry estimates of SaO2 were significantly higher than blood measurements at all times throughout exercise and no significant decrease from rest was seen until 350 W. The significant correlations between PaO2 and PAO2 with the first exercise intensity and at V˙O2peak led to the conclusion that inadequatehyperventilation is a major contributor to exercise-induced hypoxaemia.

Cytokines enhance airway smooth muscle contractility in response to acetylcholine and neurokinin A

In vivo airway hyperresponsiveness has been demonstrated following inhalation of specific cytokines in normal individuals. Whether this airway hyperresponsiveness results from a direct effect of cytokines on airway smooth muscle contractility, or via changes in airway wall structure is not known. The aim of the present study was to determine the effect of the pro‐inflammatory cytokines interleukin‐1β (IL‐1β) and tumour necrosis factor‐α (TNF‐α) on airway smooth muscle contractility in vitro.

ROLE OF TACHYKININS IN BRONCHIAL HYPER-RESPONSIVENESS

1. Sensory afferent fibres mediate important protective reflexes in the lung. Small, unmyelinated C‐fibre nerves have both sensory afferent and effector functions. C‐fibres contain a number of neuropeptides, including the tachykinins, which have proinflammatory effects in the airways. Following stimulation with capsaicin and other stimuli, neuropeptides are released from the nerve endings, either directly or by axonal reflexes.

Arterial hypoxaemia in endurance athletes is greater during running than cycling.

The effect of both training discipline and exercise modality on exercise-induced hypoxaemia (EIH) was examined in seven runners and six cyclists during 5 min high intensity treadmill and cycle exercise. There were no significant interactions between training discipline, exercise modality and arterial P(O(2)) (Pa(O(2))) when subject groups were considered separately but when pooled there were significant differences between exercise modalities. After min 2 of exercise arterial hydrogen ion concentration, minute ventilation, alveolar P(O(2)) (PA(O(2))) and Pa(O(2)) were all lower with treadmill running with the largest differential for the latter occurring at min 5 (treadmill, 80.8+/-1.8; cycle, 90.2+/-2.5, mmHg, N=13, P< or = 0.05). At every min of exercise, the differences in Pa(O(2)) between the ergometers were strongly associated with similar differences in PA(O(2)) and alveolar to arterial P(O(2)) (PA(O(2))-Pa(O(2))). It is concluded that the greater EIH with treadmill running is a consequence of the combined effect of a reduced lactic acidosis-induced hyperventilation and greater ventilation-perfusion inequality with this exercise mode.

Pre-protachykinin-A mRNA is increased in the airway epithelium of smokers with chronic bronchitis

Objective: Tachykinins are neuropeptides present in sensory nerves in the lung. Aside from their role as neurotransmitters, these peptides exert pro‐inflammatory and protective effects in the airways. Although tachykinins may be released from sensory nerves, there is increasing evidence that they are also produced by non‐neuronal cells. The nett effect of tachykinins will likely result from relative changes in the levels of tachykinins, tachykinin receptors and tachykinin degrading enzymes. We investigated whether tachykinins might be produced locally in human airway epithelium in vivo, and whether mRNA levels for either tachykinins, their receptors, or for the tachykinin degrading enzyme neutral endopeptidase (NEP) were altered in subjects with chronic bronchitis compared to normals.

A metabolite of substance P, SP7-11 is involved in the pathogenesis of inflammatory joint disease.

The possibility that neuropeptides, in particular members of the tachykinin family are involved in inflammatory joint disease is widely disputed. Both clinical and experimental observations indicate that the tachykinin substance P (SP) may be involved in the pathogenesis of arthritis. We have studied the effects of tachykinins and the metabolites of SP on chondrocyte function. We have shown that the C-terminal pentapeptide sequence; H-Phe-Phe-Gly-Leu-Met-NH2 is biologically active in bovine chondrocyte cultures. The production of SP7-11 is limited by hydrolysis of the intact peptide by neutral endopeptidase (E.C. 3.4.24.11). The regulation of this enzyme would modulate the activity of substance P on articular cartilage chondrocytes.

Interleukin-1beta and tumour necrosis factor-alpha increase microvascular leakage in the guinea pig trachea.

Objective: Airway microvascular leakage is considered to be an important component of airway inflammation in asthma. In the present study we examined the effect of interleukin‐1β (IL‐1β) and tumour necrosis factor‐α (TNFα) on airway microvascular leakage in vivo.

Tachykinin-induced bronchoconstriction in sheep is NK-1 receptor mediated and exhibits tachyphylaxis

Objective: Tachykinins are mediators of airway hyper‐reactivity and inflammation. There is in vitro evidence that ovine responses to tachykinins correlate closely to human responses. This study was designed to characterize the effect of intravenously administered tachykinins on sheep lung resistance in vivo to determine the effect of dose timing on reproducibility of responses and the induction of tachyphylaxis. We then used this information to help further characterize the response with several pharmacological agents.

Tachykinins contribute to the acute airways response to allergen in sheep actively sensitized to Ascaris suum

Abstract Tachykinins, found in sensory nerves, have effects in the airways which suggest that they may contribute to the pathogenesis of asthma. We aimed to find evidence for tachykinin involvement in the immediate airway response to allergen in a sheep model of experimental asthma. Twenty‐four sheep were actively sensitized to Ascaris suum, then challenged with nebulized Ascaris extract in a dose‐response fashion. Change in lung resistance (RL) in response to challenge was measured. Responder sheep (those with an increase in RL of >100% over baseline) that had reproducible responses over three challenges were identified (n= 4 sheep) and a PC100 (number of breaths of extract required to induce a 100% increase in RL) was determined. The effect of the neutral endopeptidase inhibitor phosphoramidon, the NK‐1 receptor‐specific antagonist CP 96, 345 and capsaicin desensitization on the RL response to Ascaris challenge was then assessed. Administration of phosphoramidon before Ascaris decreased the PC100 to 31 ± 7% of the PC100 seen with Ascaris alone (P<0.05), whereas CP 96,345 and capsaicin desensitization increased the PC100 to 285 ± 41% and 555 ± 93% respectively (P<0.05 for both). These findings suggest that endogenous tachykinins are released in response to allergen challenge and that they contribute to the immediate increase in RL.